Preliminary studies in our laboratory indicate that the enzyme-linked immunoabsorbent assay (ELISA) using antigens derived from the embryonated egg stage of Toxocara canis (TEE) is a suitable test for the diagnosis of Visceral Larva Migrans (VLM), an important zoonosis in the United States, and for seroepidemiological studies on the prevalence of T. canis antibody in human populations. The objectives of this study are to determine the validity and reliability of the ELISA in the diagnosis of acute VLM, to measure the prevalence of antibody in several populations of children (cross-sectional analysis), and to determine the control approach. These studies should enable us to assess the public health implications of environmental contamination with this nematode and to formulate recommendations for primary and secondary prevention.